Re: [boost] Re: [Filesystem] i18n

From: Beman Dawes (bdawes_at_[hidden])
Date: 2005-03-31 21:20:15

At 08:51 PM 3/31/2005, David Abrahams wrote:
 >"Peter Dimov" <pdimov_at_[hidden]> writes:
 >
 >> Beman Dawes wrote:
 >>
 >>> At 01:06 PM 3/31/2005, Rob Stewart wrote:
 >>
 >>>> I disagree.  All the caller wants to know is whether the supplied
 >>>> pathname refers to an existing file.
 >>>
 >>> But if it isn't possible to reliably answer that query, shouldn't it
 >>> be an error?
 >>
 >> The answer to this question is probably "no", if by error you mean
 >> exception, and here is why.
 >>
 >> Every exception-throwing function has spawned a predicate that is used 
to
 >
 >> avoid the exception (because exceptions cancel the currently active
 >> operation and this is undesirable in some cases).
 >
 >Separate predicates don't really help you avoid exceptions reliably in
 >filesystems because of race conditions.  But y'all know that.  Why
 >have we gone down that road...

One way of looking at the current discussion is that we are trying to avoid 
going down that road.

 >... as opposed to having an argument that can
 >be used to say "don't throw?"

The other semantics of throwing and non-throwing functions may be 
different. The importance of avoiding race conditions may be different. 
That's why I'm thinking of separate functions distinguished by function 
name rather a "don't throw" argument. However, a stat()-like function might 
have both throwing and non-throwing versions, with no other differences, so 
that might be a candidate for a throw/don't-throw argument.

--Beman